Tag Archives: relativity

How do we observe galaxies further than 13.7 billion light years away?

z8_GND_5296. Credit: V. Tilvi (Texas A&M), S. Finkelstein (UT Austin), the CANDELS team, and HST/NASA Sorry for such a lengthy title, but the subject came up because of a widely circulated announcement of the discovery of “The Most Distant Galaxy … Continue reading

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Ask a Physicist: How does Spacetime get Bent?

My latest column is up at io9: “How does Spacetime get Bent?” It’s an overview of how to think about curved spacetime, even if the universe “really” feels flat. Enjoy! -Dave

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Travel to the end of the Universe

About a week ago, I had a contest on io9 calling for questions about the universe. I got one that seems, on first blush, to be kind of silly, but on further inspection is kind of awesome. Cameron asks: What … Continue reading

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I get email: WHY (not how) does speed and mass affect time?

Credit: Herb Thornby As you may know, I’m teaching a General Relativity course this term, and so I have spacetime on the brain. So it’s particularly fun when I get relativity-oriented emails. This morning, for instance, I found a question … Continue reading

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I get mail: Does a box of photons have mass?

Lately, my my inbox hath overflowed. Yesterday, I got a thought-provoking email from a fellow physics instructor. It’s a good, non-intuitive question about special relativitiy. It’s also got the “technical” tag, so if you’re afraid of a few equations and … Continue reading

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Hawking Radiation and The Equivalence Principle

Important warning: This is just an artist’s depiction of a black hole, and what’s coming out of it certainly isn’t Hawking Radiation Black Holes are awesome. On this, I think we can all agree. But even though they are insatiable … Continue reading

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Antworld, the Equivalence Principle, and GR

I’ve been thinking a lot about Special and General Relativity lately, and in particular, the Equivalence Principle — the main theme for Chapter 7 of my upcoming book on symmetry. In the process, I started playing around with a really … Continue reading

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A symmetry approach to time dilation

Howdy, folks. As you know, I’m in the midst of writing my book on symmetry, and every now and again, I like to try to run various drafts of different snippets of the manuscript by you, the peanut gallery, for … Continue reading

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I get mail: Twin Paradox Edition

Greetings, true believers! Apologies for the relative infrequency in posting, but as most of you know, I’ve been working hard on my upcoming book. I’m over the hump, and sent the first half to my editor a couple of weeks … Continue reading

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I get email: Do FTL signals let you communicate back in time?

First and foremost, let me go on the record, once again, and say that I think that the faster than light neutrino result is almost certainly flawed. I’m not going to debate the point, since I’ve already made a number … Continue reading

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