Gravity
Tag archives for Gravity
Somethin’ Neat about our Galaxy
Posted by Ethan on March 26, 2008 So last week I was up at Pacific University in Portland, OR for a job interview. As part of a faculty interview, you have to lecture on a topic for undergraduates, but they give you the topic just a couple of days before. My topic was Gauss’ Law, which talks about the relationship between an…
Why we need Dark Matter in the Universe.
Posted by Ethan on February 19, 2008 Last week, Pamela Gay over at Star Stryder pointed me to a press release which claimed that, among other things, perhaps dark matter wasn’t necessary. So I wrote a guest post on her blog explaining why it was. Apparently, some people still aren’t convinced. So I will lay out for you all the reasons I…
What if I were made of Dark Matter?
Posted by Ethan on February 13, 2008 I’ve been talking about dark matter a lot, and yet there’s still so much to explain about it. For example, dark matter and normal matter (protons, neutrons, and electrons) have a few things in common: They both have mass. They both feel the effects of gravity. They both cause their own gravity. But that’s where…
Galaxies are made exactly how, now?
Posted by Ethan on February 13, 2008 Last week, Jamie (my significant other) came home from work and told me about a conversation she had with her coworker, Chris. This week she asked another one, Miguel, whether he had any questions about Astronomy, Physics, space, etc. This week’s question comes from Miguel: What is a galaxy, anyway? Why does it look like…
How to Build a Home in Space
Posted by Ethan on February 11, 2008 Ever get sick of your life here on Earth? What about really getting away from it all; what if you wanted to live in space, orbiting the Earth, away from everyone. (At least for awhile, like a summer home.) What would you need to do it, and what would it consist of? I propose an…
The Cosmic Microwave Background? Not always…
Posted by Ethan on February 7, 2008 The Universe isn’t a static place. Although the laws of nature (physics, chemistry, biology, etc.) don’t appear to change over time, everything in the Universe appears to evolve, and changes over time. One of the simplest ways that this happens is through Hubble expansion. General relativity tells us how the Universe expands, and more specifically,…
Dark Matter: Is it right in front of us?
Posted by Ethan on January 31, 2008 Last year, I had just finished my Ph.D. studies, and had moved to Madison, WI to teach introductory physics at the University of Wisconsin. I was working on this paper, and when I submitted it, I got a phone call from New Scientist magazine’s space division. Fast-forward two weeks, and I find this article online,…
An amazing discovery: a double Einstein Ring!
Posted by Ethan on January 24, 2008 
One of the perks of being a postdoc at a place like the University of Arizona, one of the top places in the US for astronomy, is that we get a number of really interesting visitors. Today we got paid a visit by Tommaso Treu, an astronomer at UC Santa Barbara. He spoke to us…
MOND vs. Dark Matter
Posted by Ethan on January 22, 2008 The first serious advocate of modifying Newton’s laws instead of postulating unseen (or dark) matter was Moti Milgrom, from whom today a new article appears on the astrophysics preprint archives. In particular, Milgrom asserts the following: MOND predictions imply that baryons alone accurately determine the full field of each and every individual galactic object. These…
