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 55776
How long would it take the Earth to fall into the Sun? (Intermediate) Jul 05 132834
Have astronomers observed any phenomena that could be produced by extraterrestrial civilizations? (Intermediate) May 05 49324
Why are accretion disks flat? (Intermediate) Apr 05 53265
How do we know that nuclear fusion is still going on in the Sun? (Intermediate) Jan 05 80502
Is the universe really like an expanding balloon? (Intermediate) Jan 05 81506
If gravity is a "curvature of space" rather than a force, why do a ball and bullet follow different paths? (Intermediate) Dec 04 163521
How can we understand the meaning of large numbers like "a million million?" (Beginner) Nov 04 44666
Would extraterrestrial civilizations know that there is life on Earth? (Beginner) Oct 03 49733
Will the Moon be invisible in 500 million years? (Beginner) Oct 03 67041
What is apparent magnitude? (Intermediate) Sep 03 131696
Is the universe expanding faster than the speed of light? (Intermediate) Sep 03 495562
How do we define distance in an expanding universe? (Intermediate) Aug 03 89883
When the Sun converts mass to energy, do the orbits of the planets change? (Advanced) Aug 03 120418
What is the observational difference between a star and a planet? (Beginner) Jul 03 293457
How long do supernova remnants last? (Intermediate) May 03 52769
What is the universe expanding into? (Intermediate) Apr 03 611219
How can we see galaxies if their stars are so faint? (Intermediate) Feb 03 53034
Does gravity vary across the surface of the Earth? (Intermediate) Feb 03 266816
What process would bring about a quark star? (Intermediate) Jan 03 49069
Could there be life in the galaxies nearest to the Milky Way? (Intermediate) Jan 03 137724
Does evolution contradict the second law of thermodynamics? (Intermediate) Jan 03 209244
How does the brightness of a star depend on its distance from us? (Beginner) Dec 02 91405
How do astronauts communicate with their families from space? (Beginner) Dec 02 80577
Can you see the future as you fall into a black hole? (Intermediate) Dec 02 108703
How can we see the Milky Way if we are inside it? (Intermediate) Dec 02 379503
When we look back to the Big Bang, why don't we see the universe as a tiny speck of matter? (Intermediate) Dec 02 68283
Why do astronauts in space need to exercise? (Beginner) Nov 02 54835
Why doesn't the length of each day change much around the solstices? (Intermediate) Nov 02 94870
Do we see the same stars from above and below the equator? (Beginner) Nov 02 132898
Why isn't the sky bright at night if the universe has so many stars? (Intermediate) Nov 02 232122
What are "blue stragglers" in globular clusters? (Intermediate) Nov 02 72301
How do you calculate the lifetime of the Sun? (Advanced) Nov 02 178534
How long does a solar eclipse last? (Beginner) Oct 02 168822
What companies or businesses can astronomers work for? (Beginner) Oct 02 75152
Why aren't accretion disks around giant stars as hot as accretion disks around black holes? (Advanced) Oct 02 45068
What is the farthest in space that we have gone? (Beginner) Oct 02 134180
How close does a supernova need to be to damage the Earth's environment? (Intermediate) Sep 02 53522
Is light of different colors affected differently by gravity? (Intermediate) May 02 47440
Why do clocks turn in the opposite direction from the Earth and Moon? (Intermediate) Apr 02 92077
Do most astronomers believe in God based on the available scientific evidence? (Beginner) Mar 02 132661
What can we learn from the color of a star? (Intermediate) Mar 02 179717
What happens to a substance if its speed is more than the speed of light? (Intermediate) Mar 02 148384
Will we ever stop having solar eclipses because of the moon's motion away from the Earth? (Intermediate) Feb 02 97096
Could there have been multiple Big Bangs at different places in the universe? (Intermediate) Feb 02 71158
What is the difference between the "Doppler" redshift and the "gravitational" or "cosmological" redshift? (Advanced) Feb 02 100700
How do astronauts use math in their jobs? (Beginner) Feb 02 96728
How does astronomy benefit humankind? (Beginner) Dec 01 127786
What is the physical difference between a star and a planet? (Intermediate) Sep 01 396766
Could dark energy come from matter anti-matter pairs forming spontaneously and then annihilating? (Advanced) Aug 01 49131
Can gravitational lensing from intervening galaxies cause the observed ripples in the Cosmic Microwave Background? (Advanced) Aug 01 42505
What does the term "visible universe" mean? (Beginner) Jul 01 55687
How do astronomers use math in their jobs? (Beginner) May 01 177587
What is the density of a black hole? (Advanced) Apr 01 146361
Why is the moon in a different place every night? (Beginner) Apr 01 239767
What happened to all the black holes that were around in the early universe? (Intermediate) Mar 01 47569
Why do some eclipses take longer than others? (Intermediate) Jan 01 53765
What is a star's "spectrum"? (Beginner) Oct 00 97595
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 61304

Most Popular

Our Reddit AMAs

AMA = Ask Me (Us) Anything