A Conversation with Revolutionary Scientist NEIL DEGRASSE TYSON
By Tyler Malone
“Scientists are overgrown kids,” Dr. Neil deGrasse Tyson tells me–and he’s right, scientists are the children that the rest of us adults may not realize we wish we still were. At a certain age most human beings do what is called “growing up.” What we really mean when we say “growing up” is: “becoming complacent.” As we age, we tend to become stagnant: we accept the way things are, we stop trying to learn and expand our minds, we refrain from asking questions, we cease to be curious, we stand still, we start going to our 9 to 5 jobs and suddenly the big questions no longer loom large to us.
But there are certain occupations that require a person’s inability to “grow up,” their refusal to “become complacent.” Some such professions include the artist, the writer, the philosopher–and especially the scientist. The scientist’s job is to always ask questions and, even when presented with possible answers, never be complacent with the status quo, always look for a better explanation, a more detailed understanding of our world. The scientist should go into a situation with an open mind, and let facts and data and documentable experience reveal some form of truth.
As Dr. Tyson explains, the scientist should only be one kind of -ist: that is, a scientist. All other affiliations hinder the already difficult premise of being objective. As the head of Hayden Planetarium, and as a frequent guest on shows like The Colbert Report and The Daily Show, Dr. Tyson has made it his mission to continue the legacy of Dr. Carl Sagan by bringing science to the public in an engaging way. But don’t be fooled: he’s not trying to make science interesting again, he’s trying to prove that it always was interesting in the first place. All we need is to regain our childlike sense of wonder.
I spoke with Dr. Tyson about some recent science headlines, about his hilarious late night TV show appearances, about his upcoming sequel to Carl Sagan’s iconic TV show Cosmos, and much more. We are featuring him in our Revolutionary Issue because we here at PMc Magazine find him to be a true revolutionary, but as you’ll see, he may not be entirely comfortable with that title…
Tyler Malone: How are you doing today Dr. Tyson?
Neil deGrasse Tyson: I’m well, thanks, thanks for your interest.
TM: Of course. You are truly a revolutionary, and this is for our Revolutionary Issue, so…
NDT: Alright. Me and Che Guevara, right?
TM: Ha! Exactly. So, let’s start with what was just in the news. Just last week, a neutrino was supposedly observed going faster than the speed of light. Obviously, the whole scientific community was up in arms—whether this could be true, whether it was some sort of human or mechanical error. I was wondering what your thoughts are on the possibility of such a phenomenon? If it were true, what it would mean that the speed of light is no longer the speed limit of the universe?
NDT: Actually, I posted on Facebook recently, my brief analysis of this. I ranked three possibilities in order. The first is that it is simply a mistake—that’s the most likely explanation for what happened. And from what I understand of the experiment, they repeated it multiple times and got consistent results. That’s a first step in verifying that the truly unusual result is actually real. The next step would be to have someone else try and repeat the experiment, using a different apparatus and different people. And that way, if there was a human error or an apparatus error, it would not show up a second time, we presume. It’s much less likely, and then the effect would go away. This happens all the time in science.
So what’s important to understand is that the press usually just runs after the latest experiment that’s done in the scientific community and reports it as true without reference to what’s really true, and what’s really true is whether something is verifiable by disinterested parties. Only then does the new scientific truth emerge. We’re caught in the middle of that now because the experiment hasn’t been repeated yet by a disinterested party. Most likely it’s a mistake, because we’ve gone a century without seeing anything move faster than light.
NDT: So the precedent is not in the favor of this being a real result. Two: if in fact there are neutrinos that go faster than the speed of light, then it is important to understand that going faster than speed of light is not actually precluded by Einstein’s relativity–this is widely misunderstood by the press. You can exist faster than the speed of light, you just can’t accelerate to the speed of light and then pass it. But nothing prevents you from existing faster than the speed of light. We even hypothesized a kind of particle that behaves in such a way. We called them tachyons—you can look it up on the Wiki page—tachyon, it’s from the Greek “fast.” It’s where tachometer comes from. If these are special particles that we think of as neutrinos but, in fact, they’re faster than light particles, fine, it’s just a new type of particle we’ve discovered that happily lives faster than the speed of light. And one interesting property about objects that move faster than light is that they move backwards in time. That would be fun to contemplate what it means to detect something that is moving backwards through time.
The third possibility is that it is, in fact, a new and verified result. And if it is the case, then Einstein’s relativity would need to be extended. What I mean by that, is relativity works, period. It works. If this is a regime that relativity has never previously been tested in, then we need to understand what description of the universe would enclose not only this new result, but everything that was already demonstrated that works for a century. So what that usually leads to is a deeper understanding of nature that encompasses the previous ideas. That’s what relativity was, itself, to Newton’s laws of gravity and motion.
TM: Exactly, okay.
NDT: Newton in his whole life never saw anything go faster than the racehorse. What’s that 30 miles per hour, 35 miles per hour? All his life and all of his deductions about the behavior of the universe were not tested beyond certain regimes. He came up with his laws and they worked! As our experiments became more and more invasive of nature, if you will, observing the expanding universe and the structure of the atom, what we found is that Newton’s Laws don’t really apply in these regimes. It continues to apply where it ever did apply, it’s just a new regime—so is this now a completely new law of physics that is necessary? It turns out, it was a deeper law of physics that was necessary. That is Einstein’s relativity. If you put low speed and low gravity into Einstein’s equations, those equations become Newton’s laws of gravity and motion. So it’s a deeper understanding of nature. So relativity expanded our understanding of gravity and motion, it did not replace Newtonian gravity and motion. So if there’s a way you can go faster of light, and this experiment is without precedent, then it takes us to a new place, and that’s fine, that’s good. People say, “Oh, let’s just throw Einstein out the window.” No, we’re not going to throw Einstein out the window any more than we needed to throw Newton out the window. I know that’s not a soundbite answer, but it’s the answer.
TM: That’s perfect, we don’t need soundbite answers here. Very well-explained. What are some of the greatest advances currently taking place in your particular field—in the field of astrophysics? What are some of the questions that astrophysicists are trying to tackle that seem likely that we might have some sort of answer to in the near future?
NDT: Depends what you mean by “near.” But if we say decades then possibly we’ll get some understanding of dark matter and dark energy. Dark matter: 85% of the gravity of the universe, has a point of origin about which we know nothing. Something is generating gravity in the universe that has stumped us since 1936. It used to be called “missing mass.” More recently it’s been called dark matter, but we don’t even know if it’s matter—that name is just a placeholder. Like I said, we could call it Fred and Mary, it doesn’t matter, we don’t know what it is. But we know it has gravity, and it doesn’t otherwise interact with what we are. The light doesn’t interact. We can’t observe this stuff, whatever it is, if it is stuff. Dark energy, on the other hand, is a mysterious pressure in the vacuum of space that is forcing the universe to expand faster than our laws of physics tell us it should. And we don’t know what’s causing that either—so we call it dark energy. If you add up dark matter and dark energy, as the drivers of phenomena in the universe, it comes to 96% of the universe.
TM: That’s interesting–to know how much we don’t know.
NDT: Yes, the blunt way to put it is: we are completely ignorant to what is driving 96% of the universe. The 4% that remains, that’s electrons, protons, neutrons, electrons, lights, black holes, clouds, galaxies, stars, comets, asteroids. Everything we know and love and are familiar with and have written about is 4% of the universe. Out to the edge of the universe, that’s only 4%. So, it’s a deep scientific, and in some ways philosophical problem. And we claim to know the universe as only the 4% of it that we have a handle on. So these are the biggest scientific questions that are out there, and there are others, for example, in the search for life. Is there life somewhere on Mars? Is there a record of there having once been life on Mars? And is there any other place in the solar system where there might be life as we know it? Or any other place in the galaxy where there’s a star system that would have planets, and a place to harbor life?These are questions that may get answered in the next couple decades as well.
TM: I think a lot of scientists admit that it’s likely that other life exists somewhere in the universe. Do you think it’s possible for us to ever make any sort of contact, or would that life just be too far away and too impossible to ever communicate with?
NDT: Well, you can make contact using radio waves. Radio waves travel easily through the vacuum of space. It still takes quite a while. Even if we did find pen pals somewhere, it would not be witty repartee. We’d send a message, five years later the message would arrive, and they would interpret it and decode it, and then send a message back. So we would get the reply ten years later in a case where the civilization is five years away, five light years away. But most of the interesting stars that we’re now observing are a hundreds of light years away. So a round trip signal would exceed the life expectancy of the experimenter. That’s never a good experiment to conduct. You would be dead before the results come in.
TM: As science moves forward, it seems to me, and obviously, I’m no scientist, but it seems to me that we tend to be combining the branches of science more than moving them apart from one another. I was wondering how the sciences could learn to better cross-pollinate? Or is that even something you think they need to do, or do you think they’re better as separate branches?
NDT: Perceptive of you to notice this, and my field is one of the earliest to do this in a big way. There’s such a thing as biochemistry—you can think of that as the intersection of two fields. Obviously the body has chemistry in it, so that marriage was, in many ways, expected. But there are others that aren’t expected, for example, when astrophysicists started looking at the early universe, we realized that the universe was small and hot and dense, and matter would have been broken down into component particles. We don’t have formal training in particle physics, so we knocked on the door of a particle physicist and compared notes, and said, “hey, it would do this,” or “it would behave this way,” or “you’d create these new elements or these new particles.” So thus was born astroparticlephysics. So right now, some of the leading cosmologists, the study of the origin of the universe and the evolution of the universe, have a background in particle physics. That’s a direct benefit of cross-pollination of two fields.
Not only that, we have geologists that are trying to understand the terrains of planets. We don’t actually have an official word for them, but we call them planetary geologist. But “geo” means earth, so we need a new word. But planetary geology is an entire subfield of geology. And the meetings that are held–the American Geophysical Union, that’s the professional society of which all these people are a part of–every society meeting that they have, there’s a branch that worries about planets that goes off and hangs out together. That brings the astro-folk and the geo-folk to talk about planets. Other ones: the search for life in the universe—well now, say I want to know if there’s life on Mars, but I don’t have that training, I knock on the door of a biologist, and so now we have astrobiology. So what’s great about the cross-pollination is that you get to ask questions that would not have been asked in either of the two fields that you’re joining. And typically, cross-pollinated investigations relate to origins. So if I ask what is the origin of life, I’ve got to bring in the geologist, I bring in the biologist, and I bring in the astrophysicist. Questions of origins tend to be the most diverse in the number of fields that plug into each other to arrive at an answer to a question that no one in the fields would have asked by themselves.
TM: Similarly–slightly different, but still kind of dealing with the merging–is that it’s often been stated that in order to find some sort of theory of everything, you basically have to merge general relativity and quantum theory. What are your thoughts on the possibility of that? Do you think a theory of everything is possible?
NDT: We have good precedent to presume it is, because in the past what we have found is that previously disconnected ideas of how the world worked, if those separate ideas themselves were correct, often connect in some way. Often we see that there are deeper ways to think about them where those two separate ideas are actually opposite sides of the same coin. Scientifically, philosophically, and aesthetically—in some camps, they’re driven by the beauty of nature, rather than the challenge of it. So, where was I headed there? Your question was what?
TM: Do you think it’s possible or likely that there will be a theory of everything?
NDT: Oh, right, right. There probably is one out there, the question is whether we in our hubris and audacity presume we’re smart enough to find it. Think about it, we have these brilliant string theorists who have been at it for what’s now thirty years. And back in the early days, “Oh, almost there! Almost have the answer!” Five years later, “Just a couple more years!” Five years later, “Almost there!” I’m losing patience. So why haven’t you solved it yet? “It’s a hard question…” Here’s the catch, no one of them will say, in response to that question, “Oh, we’re just too stupid to figure it out.” No, the human brain doesn’t work that way. We don’t think that way.
NDT: We think much more highly of ourselves than the defeatist notion that maybe there are things we’re just not smart enough to figure out in the universe. So that leaves the question, at what point do you give up because you know the answer isn’t there? Or at what point do you wait around till someone smarter than you is born for them to go figure it out. Or conclude that the actual solution transcends the capacity of the human mind to understand.
TM: Yes, I’ve read you’re a critic of string theory.
NDT: I’m not so much a critic, it says that on the internet somewhere, and it’s not really true. I would just say that I’m losing my enthusiasm for it. That’s not the same thing as being a critic.
I’m wondering if they’re smart, why didn’t they find it by now? And if the problem is hard, why do they think they’re smart enough to figure it out? I’m not otherwise a critic of it, it’s just, come on now, I’m getting impatient.
TM: Understandable. So, it was just a little over five years ago, 2006, August maybe, when Pluto was officially demoted from its status as a planet.
NDT: Yes, August 2006, that’s correct.
TM: You wrote a book called The Pluto Files, which documented the story of the planet Pluto and how it has captured the American imagination. I actually saw you speak a few years ago at the Barnes and Noble in Union Square when The Pluto FIles came out in paper back.
NDT: Oh yeah, there was a nice crowd there.
TM: I wonder what was it about the story of Pluto though that captured your attention and imagination?
NDT: Oh, no, I was minding my own business; it’s what captures the attention and imagination of the public. Yeah, I was happy just going on about my life. I was dragged into this. Simply because of our decision to group Pluto with its icy brethren in the outer solar system in our public exhibits. It was the reaction to those exhibits that dragged me into the ring, the boxing ring, with Pluto. So when you ask what was my love affair with Pluto? I’m actually quite indifferent.
TM: Okay, then, what do you think–I mean, obviously, this is what your book about–but in a shorter version, what do you think is the American preoccupation with Pluto, why do you think we are so fascinated with it?
NDT: I think it’s because of the dog that shares the same name. And the dog was sketched the same year that Pluto the cosmic object was discovered. So they have the same tenure in the hearts and minds of the public. And Disney named Mickey’s dog after Pluto. And so there you have it, the recipe is in place for a nation that, for any other scientific field, would not weigh in at all, but for this subject, and that subfield, there it is, the recipe is in place for people to then react emotionally to any decision that relates to Pluto.
TM: I read somewhere that actually the majority of people though still consider Pluto a planet. And then, I think that also piggybacks on, maybe a little bit of the fact that the American public, so much more so than other developed nations, doesn’t believe in evolution, and doesn’t believe in the Big Bang. And I’m wondering, how do we change that?How do scientists change that? And how do we as a country further educate our citizens and give them some sort of faith, for lack of a better word, in science? How do we make them believe what scientists tell us?
NDT: Yeah, I think the problem is–well, there’s blame to go around in all camps. The public should not simply believe what a scientist says. The public should be trained so that they can interpret what a scientist says. That’s a different kind of education. If someone stands up with degree initials listed after their name, and says something, they’re perfectly capable of saying a boneheaded thing.
And so, it’s the task of the electorate to make the judgment, to evaluate any of the things people tell you. And we are bombarded by pundits on the 24/7 news channels, and so without skepticism within you, you’re a pinball batted back and forth by all the forces that are exterior to you.
TM: Right, so what do you think we could do to improve science education?
NDT: Adults are in the way of children. Children are born explorers of the natural world around them, and we tend to restrict that expression of curiosity.
TM: I think that’s definitely true.
NDT: If we get out of their way, the kids never lose that kind of curiosity. And that’s what scientists are. Scientists are just overgrown kids, because we still want to take apart the box. We still want to dig up the worm, still want to see what’s under the rock, still want to know how it all got here.
TM: You mentioned the 24/7 the news cycle and pundits. I know, earlier this year, you were on The Colbert Report, and you took on the classic “god of gaps” argument that Bill O’Reilly put forward. Though I think you and I both see flaws in the “god of gaps” argument, O’Reilly’s version was particularly flawed because he couldn’t even put forth an adequate gap.
TM: But I loved one thing you said in an interview I saw with you, a previous interview watched online. You said, “If you take on this god of gaps argument, god becomes an ever-receding pocket of scientific ignorance.” I absolutely loved that line, it’s phenomenal.
NDT: Yeah, I barely remembered even saying that. I had to look at the clip and I said, “Holy shit, that’s a good sentence.”
TM: It really is. It’s a writer’s dream sentence.
NDT: Right, yeah, so, it was better than I could have even conjured up on the spot again. But, the sentence is correct and accurate.
TM: I wondered if you are at all a deist? Do you believe in Einstein’s or Spinoza’s god? Or do you believe in no god at all? Are you agnostic? I’m assuming you’re not a theist and don’t believe in an intervening god. Forgive me if I’m assuming too much.
NDT: Well, other than being a scientist, I’m not any other kind of -ist. These -ists and -isms are philosophies; they’re philosophy portfolios that people attach themselves to and then the philosophy does the thinking for you, instead of you doing the thinking yourself.
TM: I couldn’t agree more.
NDT: So that’s why you don’t see me claiming any of those. I don’t’ claim association with any formal organization.
I got a humanist award from the American Humanist Society. I said: “If the award has the word humanist in it, I’m not interested.” It turned out, just coincidentally, that I didn’t get an award with the word humanist in it, I got the “Science Educator of the Year Award” or something, so I said: “Okay, I’m happy to take that.”
See, what happens is, once you say you’re one thing or another, that completes half the conversation you might have had with a person, because they would then assume that everything that’s in that package is true for you. And then there’s no conversation anymore. If you’re already going to object to it, then they pre-object. I’d rather just have the conversation, so you can both still learn something from each other. Unless you’re so wrapped up in the pre-written philosophy that you have no ideas of your own at all.
So to answer your question, I will not answer it as what philosophy I subscribe to, I will simply say that, if you ask me, am I convinced that there is an all-knowing, all-powerful deity that is either in charge of the daily affairs man, or in charge of the universe, or hatched the universe: I see no evidence for it, so I’m not convinced. And in particular, I don’t see evidence for a creator who is benevolent. I just don’t see that. If you look at the level of death and destruction that natural forces wreak upon humans, if somebody’s in charge, the health and longevity of humans cannot possibly be a priority. If you want to say there’s a God, okay, I’m not even going to argue with you about that. But don’t then say that God is benevolent, the evidence doesn’t support it. Say something else. Say God makes earthquakes to remind us he’s in charge. I have no rebuttal for that. Good to go, alright, that God I’ve got evidence for.
TM: Another thing you’ve said that I absolutely love, you said, “Science is something to be proud of, it allows us to understand the world in spite of ourselves.” And then you’ve also talked about how you’re very fascinated with how the brain fools us, and how science and mathematics show us that we need to abandon our senses to find answers outside of ourselves. I was wondering if you could expand upon that, or explain how science maybe started with using our five senses, but has become so much beyond that.
NDT: Science isn’t about simply using our five senses; science is actually about subtracting away our five senses from the world. The five senses are hugely susceptible to error and delusion and deception, self-deception. We know this, physiologists have known this forever. And we’ve know it from experiments that have gone bad, or gone wrong, simply because the person has bias that they bring to the table. So science at it’s best invokes methods and tools that completely replace the senses that we bring to the table and bring other senses that don’t even exist within our biological form. And it’s that application that defines the success of science since the industrial revolution.
TM: One thing I really wanted to talk to you about: I recently read in the news that you would be hosting the long-awaited sequel to Carl Sagan’s Cosmos. I was wondering if you could tell us how that came about and when you think it will air and give us any information you can on it.
NDT: Well, I met Carl Sagan’s widow shortly–I may have met her earlier, but my first meaningful with her was shortly after Carl Sagan’s death, when she was on the board of the Planetary Society, the organization founded by Carl Sagan and others to promote awareness and support for space exploration as a fundamental part of what it is to be human. I was invited to join the board and we got to know each other, and it was clear from then that the time would come to re-do Cosmos in a way that can serve the next generation’s interest. And as my visibility grew to take on a scale that people hadn’t seen since the original Cosmos, then in some ways I became kind of the heir apparent. Especially since my life intersected with that of Carl when I was in high school and given a tour of the Cornell campus. It’s also on YouTube as well, which would be pretty easy to find. And so, you get that sort of intersection of those crossed world lines, as it were, early on, and what has come of my life since then. And Ann Druyan, who is one of the creative principals of the original Cosmos, as well as Steve Soter, a colleague of mine, who both worked on the original Cosmos, the three of us have teamed together along with a very savvy media business person, Mitchell Canold. So the four of us banded together, and said: “Let’s do this thing. Let’s figure it out, let’s conceive of it.”
So we started carrying it around to various possible networks. And in the end, many years later, after a lot of conversations, and a lot of traveling back and forth, and a lot of script treatments shared and commented upon, we landed at Fox–of all places, Fox. And that came about because I became latter day friends with Seth McFarlane, who’s a big fan of bringing science to entertainment media. I met him at a science entertainment conference in the Los Angeles area. We met, he knew my work, and shortly after he came through town, came through New York, and said, “Let’s have lunch.” And that’s when he asked if there’s anything he can do in the service of science. He was wondering if he could fund an experiment that somebody might do. I said that we have government funds for that. I then proposed: “But here’s something you could do, if you really want to make a difference, we’re looking to fund Cosmos.” He remembered Cosmos, he’s a fan of Cosmos, and he’s a fan of my work. So he said: “Let me try to bring it to Fox.”
I said, “You’ve got to be crazy, Fox?” And then I realized–it took me about thirty seconds to realize–more television-watching demographics intersect on the Fox Network than any other network I know of. They’ve got all the conservative commentary that goes on on Fox News. They’ve got liberal civic commentary that unfolds on The Simpsons and Family Guy. They’ve got the critically-acclaimed evening dramas. They’ve got Fox Sports. They’ve got Fox Searchlight pictures, which is a critically-acclaimed indie branch of 20th Century Fox. Those are the indie films that brought us Slumdog Millionaire, and Little Miss Sunshine, and Juno. 20th Century Fox’s most recent blockbuster was Avatar, which is completely scientifically-infused storytelling, and science fiction. And so this organization is more than just what the Fox News people are saying and doing. It is huge, and huge in a way that serves the multiple demographics in the nation. If you want to bring science to the public in the most visible way imagined, then Fox became the single and obvious choice—we brought it to their higher-ups, and they embraced it, and so we’re off and running now.
TM: Great, that’s wonderful to hear. I mentioned earlier, we’re interviewing you for the Revolutionary Issue because we–
NDT: Oh, by the way, I don’t see myself as a revolutionary. I think Carl Sagan is revolutionary. I am evolutionary in his footsteps, rather than being revolutionary. That’s how I see myself. He created a whole way of thinking about science, that not everyone does, not even most educators do. It’s not: “Here’s the way of science, learn it!” It’s: “Here’s what science means to you, here’s how science has influenced culture, and here are reasons why we’re all better off if you embrace this way of looking at the world,” and you fold that into the great fun scientific discoveries, but it transforms science from just a subject that you’re learning encyclopedia articles on, a subject driven by encyclopedic information, to a subject that you then embrace as part of what it is to be human. And that’s a tradition that I will continue into the 21st century.
TM: That’s actually the most perfect answer to the question that I didn’t even finish asking, because I was going to ask, who do you consider revolutionary…and there you have it! So…
NDT: Right, well, in the science-education realm, undoubtedly, Carl Sagan. A true revolution is, when it’s done, you look at it and say: “Well, okay, that was obvious. Of course it had to be that.” Because it was a need you didn’t know you had.
TM: Right. Okay, so my last question: What is the one cosmological question that you’re most intrigued by, and what revolutions would take place if we were to discover the answer?
NDT: If there’s life in our solar system, or nearby, even if it’s not in our solar system. And if so, is it DNA-based. It would be exciting if it’s not DNA-based, but it would still be fun if it were. If it were DNA-based, it would probably mean that we’re all related. That microbes transported from planet to planet, we found ways that that can happen.
MT: Oh, interesting.
NDT: It would, in fact, be inevitable. And so then, it’s not interesting, it’s just life planet-hopping. Microbial life stowing away on rocks flung into space from asteroid impacts. So that’s one angle on it. If life is not DNA-based, that would demonstrate that life has a strong chemical propensity to get made, and that there’s more than one way of making it, so that would be–those are the two, I think, significant revolutionary advances that we await.
MT: Definitely. Well, thank you, thank you very much for this interview.
Okay, well, good luck with that. It should be fun, and send us a link when you get it so we can spread the love.
Of course, definitely will. Have a great day, and I look forward to seeing you on Real Time with Bill Maher or The Colbert Report soon.
Oh, yeah, yeah. I try to stay home, you know, but if they call me, I come.
Neil deGrasse Tyson interviewed by Tyler Malone
Written by Tyler Malone
Photography by Patrick McMullan & Clint Spaulding for Patrick McMullan.com
Design by Marie Havens
Neil deGrasse Tyson, THE SCHOOL OF AMERICAN BALLET Workshop Performance Benefit, The School of American Ballet, Lincoln Center, NYC, June 8, 2010, Photography by Clint Spaulding for Patrick McMullan.com
Neil deGrasse Tyson, TIME Magazine’s 100 Most Influential People 2007, Jazz at Lincoln Center, NYC, May 8, 2007, Photography by Patrick McMullan for Patrick McMullan.com