Ask an Astronomer Team

Dave Rothstein

Dave is a former graduate student and postdoctoral researcher at Cornell who used infrared and X-ray observations and theoretical computer models to study accreting black holes in our Galaxy. He also did most of the development for the former version of the site.

Display # 
Title Created Date Hits
When measuring the expansion of the universe, do astronomers consider that they're seeing how galaxies moved long ago, not today? (Intermediate) Jan 08 67931
How long would it take the Earth to fall into the Sun? (Intermediate) Jul 05 154234
Have astronomers observed any phenomena that could be produced by extraterrestrial civilizations? (Intermediate) May 05 58698
Why are accretion disks flat? (Intermediate) Apr 05 67085
How do we know that nuclear fusion is still going on in the Sun? (Intermediate) Jan 05 95703
Is the universe really like an expanding balloon? (Intermediate) Jan 05 99481
If gravity is a "curvature of space" rather than a force, why do a ball and bullet follow different paths? (Intermediate) Dec 04 203029
How can we understand the meaning of large numbers like "a million million?" (Beginner) Nov 04 52480
Would extraterrestrial civilizations know that there is life on Earth? (Beginner) Oct 03 57733
Will the Moon be invisible in 500 million years? (Beginner) Oct 03 77755
What is apparent magnitude? (Intermediate) Sep 03 143310
Is the universe expanding faster than the speed of light? (Intermediate) Sep 03 543315
How do we define distance in an expanding universe? (Intermediate) Aug 03 106391
When the Sun converts mass to energy, do the orbits of the planets change? (Advanced) Aug 03 137154
What is the observational difference between a star and a planet? (Beginner) Jul 03 327502
How long do supernova remnants last? (Intermediate) May 03 61529
What is the universe expanding into? (Intermediate) Apr 03 692126
How can we see galaxies if their stars are so faint? (Intermediate) Feb 03 61420
Does gravity vary across the surface of the Earth? (Intermediate) Feb 03 336633
What process would bring about a quark star? (Intermediate) Jan 03 57561
Could there be life in the galaxies nearest to the Milky Way? (Intermediate) Jan 03 153884
Does evolution contradict the second law of thermodynamics? (Intermediate) Jan 03 234192
How does the brightness of a star depend on its distance from us? (Beginner) Dec 02 110960
How do astronauts communicate with their families from space? (Beginner) Dec 02 93238
Can you see the future as you fall into a black hole? (Intermediate) Dec 02 141254
How can we see the Milky Way if we are inside it? (Intermediate) Dec 02 426559
When we look back to the Big Bang, why don't we see the universe as a tiny speck of matter? (Intermediate) Dec 02 77550
Why do astronauts in space need to exercise? (Beginner) Nov 02 61365
Why doesn't the length of each day change much around the solstices? (Intermediate) Nov 02 106004
Do we see the same stars from above and below the equator? (Beginner) Nov 02 166755
Why isn't the sky bright at night if the universe has so many stars? (Intermediate) Nov 02 250479
What are "blue stragglers" in globular clusters? (Intermediate) Nov 02 81698
How do you calculate the lifetime of the Sun? (Advanced) Nov 02 206361
How long does a solar eclipse last? (Beginner) Oct 02 181191
What companies or businesses can astronomers work for? (Beginner) Oct 02 86191
Why aren't accretion disks around giant stars as hot as accretion disks around black holes? (Advanced) Oct 02 52647
What is the farthest in space that we have gone? (Beginner) Oct 02 163504
How close does a supernova need to be to damage the Earth's environment? (Intermediate) Sep 02 62704
Is light of different colors affected differently by gravity? (Intermediate) May 02 57016
Why do clocks turn in the opposite direction from the Earth and Moon? (Intermediate) Apr 02 114999
Do most astronomers believe in God based on the available scientific evidence? (Beginner) Mar 02 159752
What can we learn from the color of a star? (Intermediate) Mar 02 226232
What happens to a substance if its speed is more than the speed of light? (Intermediate) Mar 02 178541
Will we ever stop having solar eclipses because of the moon's motion away from the Earth? (Intermediate) Feb 02 108886
Could there have been multiple Big Bangs at different places in the universe? (Intermediate) Feb 02 82569
What is the difference between the "Doppler" redshift and the "gravitational" or "cosmological" redshift? (Advanced) Feb 02 121568
How do astronauts use math in their jobs? (Beginner) Feb 02 106426
How does astronomy benefit humankind? (Beginner) Dec 01 146460
What is the physical difference between a star and a planet? (Intermediate) Sep 01 442864
Could dark energy come from matter anti-matter pairs forming spontaneously and then annihilating? (Advanced) Aug 01 57286
Can gravitational lensing from intervening galaxies cause the observed ripples in the Cosmic Microwave Background? (Advanced) Aug 01 49163
What does the term "visible universe" mean? (Beginner) Jul 01 64488
How do astronomers use math in their jobs? (Beginner) May 01 202163
What is the density of a black hole? (Advanced) Apr 01 167476
Why is the moon in a different place every night? (Beginner) Apr 01 297035
What happened to all the black holes that were around in the early universe? (Intermediate) Mar 01 54275
Why do some eclipses take longer than others? (Intermediate) Jan 01 64216
What is a star's "spectrum"? (Beginner) Oct 00 112905
How can we distinguish a star's "real" color from the change in color that we observe due to the star's motion? (Intermediate) Oct 00 71700

Most Popular


Our Reddit AMAs

AMA = Ask Me (Us) Anything