Ask Us

For information on how to do a web search, see the "Imagine the Universe!" page How to Search the Web... (and Actually Find What You Want).

Beth Barbier
(September 2003)

From Webster's dictionary:

1. Pertaining to the Universe, and having special reference to universal law or order, or to the one grand harmonious system of things; hence; harmonious; orderly.
2. Pertaining to the solar system as a whole, and not to the Earth alone.
3. Characteristic of the cosmos or Universe; inconceivably great; vast; as, cosmic speed.

In our web site name, it's a reference to cosmic rays, which can come from outside as well as inside the heliosphere.

Beth Barbier
(August 2000)

You might be able to find your answer by looking through NASA's web site on Astrobiology.

Beth Barbier
(December 2006)

With a quick search on Google for "milky way" and "named by", I was able to find that our sister web site, Imagine the Universe!, has already answered this question. You can find their answer at: Naming of the Milky Way.

Beth Barbier
(October 2002)

Sure there have been supernovae in our Galaxy (typically one every 100 years). The two most famous in our Galaxy are the "Crab" of 1054 in the constellation Taurus, and Tycho's supernova of 1572 (in the constellation Cassiopeia). Also, in 1987, a supernova was detected in a neighbor galaxy of ours, the Large Magellanic Cloud. This is referred to as Supernova 1987a.

Dr. Louis Barbier

Comet Halley is in orbit about the Sun. The orbit is very elliptical (like a squashed circle) and takes the comet from inside the orbit of Venus to beyond the orbit of Neptune. It is only when the comet is close to the Sun that we can see it, because the heat from the Sun boils off part of the comet (which is something like a mix of ice, dry ice (CO2), and dirt), and lights up the dust and gas that is boiling off. As you guessed, one orbit takes about 77 years. For more information, you can check Views of the Solar System.

Dr. Eric Christian
(May 2000)

The best way to explain it is to use an analogy that you possibly have seen. If you think of space as a thin sheet of rubber (think of the material of a balloon stretched over a frame), then putting object with mass will dimple the material, and the more the mass, the deeper the dimple. These dimples are analogies to "gravitation wells".

When a comet gets closer to the Sun (perihelion), it is effectively falling "downhill" and it picks up speed. As it gets farther, it is working its way "uphill" and gets slower. More technically, what is happening for a comet heading towards aphelion (and a ball rolling up a hill) is that kinetic energy (the energy of motion) is being converted into gravitational potential energy. It loses kinetic energy by slowing down, but that energy is stored as potential.

The next question is usually why the comet doesn't roll right downhill into the Sun. The answer is that it has enough sideways velocity to roll around the gravitational well without falling in. This is true of anything that is "in orbit" around another object. The comet would have to slow down to fall into the Sun. Correspondingly, the space shuttle has to fire its rockets to slow down in order to come back to Earth.

Dr. Eric Christian
(December 2005)

A meteoroid is a rock, whereas a comet is more like a snowball, although most of the ice is not water ice. When a comet gets close to the Sun, it starts to melt, and the gas that is given off glows, giving you a comet tail. Meteoroids are very difficult to see unless they enter the Earth's atmosphere, when they heat up and give a bright streak in the sky. It is the streak that is called a meteor. If any part of the meteoroid survives to hit the ground (most don't), it's called a meteorite.

Dr. Eric Christian
(March 2000)

This is true only for falling stars that come from the Leonid meteor shower. The Perseids point towards Perseus, etc. The reason is that these showers are due to dust remaining in the path of comets (the Leonids are due to comet P/Tempel-Tuttle for example). The direction the shooting stars come from is the direction of the comet orbit when the Earth's orbit crosses it.

Dr. Eric Christian

The Leonid meteor storm on Nov. 17th is the dust trail of comet Tempel-Tuttle. Most of the particles are a little smaller than a grain of sand and a lot of them hit the Earth and burn up in the atmosphere, causing the shower, but there are very few rocks big enough to reach the ground and almost certainly nothing of a size to cause a major problem on Earth (the comet is just too small). However, satellites are much more at risk, having no atmosphere to protect them. These particles are moving extremely fast (> 400,000 mph) and have the kinetic energy of a .45 caliber bullet. But no satellites were hit during the 1998 shower.

Dr. Eric Christian

The answer is Hermann Oberth. There's a very short biography of him on Biography.com.

Beth Barbier
(August 2000)

There's one at StarChild that shows this nicely.

Beth Barbier

In some ways our Galaxy is hard to study (because we are living in the middle of it, so to speak), but in many ways it's very easy to study (because we are living in the middle of it!) All of those pictures that you see of entire galaxies are never of our Galaxy. We do not have the ability to get outside our Galaxy and take a picture of it. We can look through our Galaxy in all directions and then make a composite "picture", inferring the structure, but we cannot take our Galaxy's picture in the conventional sense.

Dr. Louis Barbier

Try looking on this Scientific American web site.

Dr. Louis Barbier

I believe that what you are describing is termed "magnetic levitation". The effect doesn't really give zero gravity, but, more properly, a strong enough magnetic field can produce a force on an object which is equal and opposite to the gravitational force, to make an object levitate. This is due to the effects of the magnetic field on the constituent molecules and atoms of the object.

A couple of good links:

Magnetic Levitation - Science is Fun
The Frog That Learned to Fly

Dr. Randy Jokipii
(May 2003)

I have an idea for a car that isn't environmentally hazardous. Since the same poles (North or South) of two magnets repel each other, we could pave the roads with magnetic fields, and the cars would have magnets under them to propel them off the road. Would this work?

It doesn't work exactly this way, but this technology is already in development. Unfortunately, it would take an impossibly large magnet or a huge amount of electricity to generate a magnetic field on our highways, which makes it impractical. But there are several other ways to use the technology. Here's an example of how NASA is trying it out.

Beth Barbier

The KSC Space Shop has materials for purchase: The Space Shop

Beth Barbier
(May 2005)

There's no way I can know what newsletter you were receiving, but NASA's Office of Space Science sends an email newsletter out. Information on this is at: Get News by E-Mail

Beth Barbier
(January 2003)

There is some politics in everything mankind does, but here at NASA there is probably more politics in the selection of which missions and science are pursued than in the dissemination of knowledge. Many of us scientists would rebel if there was really some conspiracy to keep knowledge (aliens, face on Mars, whatever) from the general public.

Dr. Eric Christian

There is a NASA web site with some science fair project suggestions from the IMAGE mission.

Some ideas related to the ACE spacecraft:

• There's an activity entitled Interpreting Realtime ACE Data From Space that might be used as a basis for a project. Within that abstract is a link to an educational brief about ACE and its mission.
• If you want to know more about the Advanced Composition Explorer (ACE) spacecraft, a great place to start is on ACE home page.

If you want more information about cosmic rays and heliospheric science, start with Cosmicopia.

Beth Barbier

It depends upon whether you mean meteorites and other falling space debris or garbage that the astronauts bring back. Most infalling debris is small (grain of sand or smaller) and burns up in the atmosphere. Only an occasional chunk is large enough to survive re-entry, and then it hits the ground as a meteorite.

The astronauts bring back their garbage on the shuttle, or in the case of the cosmonauts on MIR, they have unmanned supply capsules that are loaded with garbage on their return mission.

Dr. Eric Christian

It's an interesting theory, but at some level, it falls more under the category of philosophy than science (not that they are totally separate!) To have a scientific theory, you have to show that it explains our observations as well or better than our current theories, and preferably, that it can make predictions that can be tested. No time travel is already pretty well handled by our concepts of causality. But general relativity has consequences for different observers such as the lack of simultaneity, that have been tested and fit in well with theories that have a well defined past.

Dr. Eric Christian

This is, of course, a hoax. Check out the Skeptic's Dictionary for a good discussion of this.

Dr. Eric Christian
(December 2001)

This question is philosophy, not physics, but the historical evidence is that we will eventually die out or evolve into something that is no longer "mankind". In the long run, nature always wins.

Dr. Eric Christian
(August 2000)

I don't want to get into questions that are more philosophical than scientific, but I do have a few comments:

1. If the human soul is pure energy, it is of a type that is unmeasurable by modern science.
2. Energy does not need to be replenished. Energy is constant. The Sun's fusion burns mass energy to light and heat, but the total energy is not created or destroyed, just changed.
3. Chemical reactions are very well understood, and there is no missing energy generated that could create/replenish/whatever a soul.

Dr. Eric Christian

According to Webster's Dictionary, astrology is "the art of judging of the influences of the stars upon human affairs, and of foretelling events by their position and aspects." Astronomy is the "scientific study of the universe around us, everything outside of the Earth's atmosphere." Astronomy is a science, while astrology is described generously as an art. It is easy to show that where the doctors and nurses were in the room when you were born has more effect on you than where the planets were in their orbits. Some astrologers even fake orbital calculations to impress their clients.

Your question has come to NASA, and I'm sure you know that we answer scientific questions. Science is "any domain of knowledge accumulated by systematic study and organized by general principles". Many people erroneously believe that astrology is a science, and it is often advertised as such. Hundreds of years ago, it was considered science by many, many people. Systematic study over the centuries has shown that astrology is not based in any way on scientific fact.

Beth Barbier and Dr. Eric Christian

Neither Tom Cruise nor scientology had anything to do with the glossary. That's all ours.

Beth Barbier
(January 2008)

This is such an obviously silly hoax that even Christian websites have debunked it and tried to stop its spread, but to no avail. For more info, check our sister website "Imagine the Universe" for Can Science Confirm the Missing Day Referred to in the Bible? and the links listed there.

Dr. Eric Christian
(March 2002)

I use "spacecraft" and Webster's Dictionary agrees with me.

Dr. Eric Christian
(May 2002)

The best response to your question is to suggest you look on the Bad Astronomy website for Phil Plait's review of the movie.

He is a NASA scientist and covers the validity of many of the specifics of the science shown in the movie.

Beth Barbier
(October 2003)