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.

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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 60931
How long would it take the Earth to fall into the Sun? (Intermediate) Jul 05 141602
Have astronomers observed any phenomena that could be produced by extraterrestrial civilizations? (Intermediate) May 05 53435
Why are accretion disks flat? (Intermediate) Apr 05 60851
How do we know that nuclear fusion is still going on in the Sun? (Intermediate) Jan 05 86820
Is the universe really like an expanding balloon? (Intermediate) Jan 05 89611
If gravity is a "curvature of space" rather than a force, why do a ball and bullet follow different paths? (Intermediate) Dec 04 181181
How can we understand the meaning of large numbers like "a million million?" (Beginner) Nov 04 47987
Would extraterrestrial civilizations know that there is life on Earth? (Beginner) Oct 03 53217
Will the Moon be invisible in 500 million years? (Beginner) Oct 03 71287
What is apparent magnitude? (Intermediate) Sep 03 136670
Is the universe expanding faster than the speed of light? (Intermediate) Sep 03 516119
How do we define distance in an expanding universe? (Intermediate) Aug 03 97072
When the Sun converts mass to energy, do the orbits of the planets change? (Advanced) Aug 03 126798
What is the observational difference between a star and a planet? (Beginner) Jul 03 309117
How long do supernova remnants last? (Intermediate) May 03 56816
What is the universe expanding into? (Intermediate) Apr 03 640364
How can we see galaxies if their stars are so faint? (Intermediate) Feb 03 56676
Does gravity vary across the surface of the Earth? (Intermediate) Feb 03 296946
What process would bring about a quark star? (Intermediate) Jan 03 52870
Could there be life in the galaxies nearest to the Milky Way? (Intermediate) Jan 03 144820
Does evolution contradict the second law of thermodynamics? (Intermediate) Jan 03 220680
How does the brightness of a star depend on its distance from us? (Beginner) Dec 02 99305
How do astronauts communicate with their families from space? (Beginner) Dec 02 86414
Can you see the future as you fall into a black hole? (Intermediate) Dec 02 124379
How can we see the Milky Way if we are inside it? (Intermediate) Dec 02 398911
When we look back to the Big Bang, why don't we see the universe as a tiny speck of matter? (Intermediate) Dec 02 72503
Why do astronauts in space need to exercise? (Beginner) Nov 02 57628
Why doesn't the length of each day change much around the solstices? (Intermediate) Nov 02 99606
Do we see the same stars from above and below the equator? (Beginner) Nov 02 147143
Why isn't the sky bright at night if the universe has so many stars? (Intermediate) Nov 02 240490
What are "blue stragglers" in globular clusters? (Intermediate) Nov 02 76441
How do you calculate the lifetime of the Sun? (Advanced) Nov 02 189647
How long does a solar eclipse last? (Beginner) Oct 02 173695
What companies or businesses can astronomers work for? (Beginner) Oct 02 80022
Why aren't accretion disks around giant stars as hot as accretion disks around black holes? (Advanced) Oct 02 48578
What is the farthest in space that we have gone? (Beginner) Oct 02 148935
How close does a supernova need to be to damage the Earth's environment? (Intermediate) Sep 02 57335
Is light of different colors affected differently by gravity? (Intermediate) May 02 51432
Why do clocks turn in the opposite direction from the Earth and Moon? (Intermediate) Apr 02 100694
Do most astronomers believe in God based on the available scientific evidence? (Beginner) Mar 02 142594
What can we learn from the color of a star? (Intermediate) Mar 02 201265
What happens to a substance if its speed is more than the speed of light? (Intermediate) Mar 02 160943
Will we ever stop having solar eclipses because of the moon's motion away from the Earth? (Intermediate) Feb 02 102108
Could there have been multiple Big Bangs at different places in the universe? (Intermediate) Feb 02 76232
What is the difference between the "Doppler" redshift and the "gravitational" or "cosmological" redshift? (Advanced) Feb 02 109866
How do astronauts use math in their jobs? (Beginner) Feb 02 100822
How does astronomy benefit humankind? (Beginner) Dec 01 136475
What is the physical difference between a star and a planet? (Intermediate) Sep 01 417318
Could dark energy come from matter anti-matter pairs forming spontaneously and then annihilating? (Advanced) Aug 01 52573
Can gravitational lensing from intervening galaxies cause the observed ripples in the Cosmic Microwave Background? (Advanced) Aug 01 45434
What does the term "visible universe" mean? (Beginner) Jul 01 59472
How do astronomers use math in their jobs? (Beginner) May 01 187483
What is the density of a black hole? (Advanced) Apr 01 156059
Why is the moon in a different place every night? (Beginner) Apr 01 260685
What happened to all the black holes that were around in the early universe? (Intermediate) Mar 01 50504
Why do some eclipses take longer than others? (Intermediate) Jan 01 57824
What is a star's "spectrum"? (Beginner) Oct 00 104253
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 65715

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