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Archive: April 2011

Science and the Human Mind

April 27, 2011 by Mario Livio

blog_2011_04_27bRecently I visited Israel, and while there, I participated in a TV program entitled: “Worth A Thought.”

The concept is rather interesting. Each program in this series consists of two people having a conversation for half an hour. The program covers a wide variety of topics — recent discussions ranged from the Israeli healthcare system to Arab culture.

I was asked to have a conversation with Dr. Robert Aumann, a mathematician who won the Nobel Prize in Economics in 2005. We were supposed to talk about the nature of mathematics and its role as the language of science, but the conversation wandered into the nature of science in general.

In particular, we both agreed that while there is no doubt that some physical reality independent of humans exists out there (Otherwise, as Woody Allen once said: “If nothing really exists, I definitely overpaid for my last carpet”), our DESCRIPTION of that reality — what we call “science” — is heavily influenced by human perception and concepts.

As an example, take a simple statement such as: We are held by the force of gravity onto a sphere called Earth. This statement is loaded with concepts that are creations of the human mind. What is a sphere? It is the collection of all the points that are at an equal distance from a certain point in space. But what is a point? What is distance? What is space? What is a force?

Aumann and I also agreed, however, that the human endeavor to uncover the “laws of nature” would not have been possible at all had such laws not existed in the first pace. In other words, if a hydrogen atom on Earth behaved very differently from a hydrogen atom in a galaxy that is a million light years away, or if the results of experiments in Alabama produced entirely different results from those of the same experiments carried out in New Mexico, all our attempts to understand the universe would have been doomed.

Nature has been kind to us, being governed by universal laws, rather than by some parochial bylaws. This way, even with our biased human minds, we have a chance at deciphering Nature’s grand design.

Surprisingly Young or Surprisingly Old?

April 20, 2011 by Frank Summers
Galaxy Cluster Abell 383

Galaxy Cluster Abell 383

On April 12, 2011, HubbleSite published a press release with a headline mentioning a “surprisingly young” galaxy.

My first reaction was to think, shouldn’t that be “surprisingly old?” You really can think of it both ways, and I can see how it would be confusing to the public, so let me explain.

The press release explains that Hubble helped discover a faint galaxy with a large redshift. The measured redshift can be converted to a distance, and that distance turns out to be about 12.75 billion light-years. Since a “light-year” is the distance light can travel in one year, the light from this galaxy has traveled for 12.75 billion years before being observed by Hubble.

That means we see the galaxy as it was 12.75 billion years ago. Since the universe is only about 13.7 billion years old, this is a galaxy that was present 950 million years after the big bang. That’s “surprisingly young” in the lifetime of the universe for a galaxy to have formed.

However, that is not the most distant or earliest galaxy that Hubble has ever seen. A candidate for the most distant galaxy was recently announced, and its distance is about 13.2 billion light-years. So what makes this new observation in any way surprising? That’s where we get into the old part.

In the galaxy at 12.75 billion light-years, the stars are estimated to be about 750 million years old. That makes this galaxy relatively fully formed, while other such distant galaxies appear to have stars that are just forming at the time we see them. Subtracting 750 million from 950 million, you find that these stars seem to have formed around 200 million years after the big bang. THAT is the really surprising part. Astronomers do not expect so many stars to form so quickly after the start of the universe. Hence, given that the galaxy is seen 950 million years into the universe, its stars are “surprisingly old.”

It can get confusing when you think about these matters dealing with our time-warped view of the universe. We see distant objects not as they are today, but as they were at a time long ago. And that time is different for each object, because it depends on the distance to each object. The intriguing point for astronomers is that we can look out into space, and back into time, and see the history of how galaxies developed. This new observation indicates that such development may have started a couple hundred million years earlier than we expected.

Reflections on Beta Pictoris

April 13, 2011 by Ray Villard
This Hubble Space Telescope view of Beta Pictoris shows a main dust disk and a much fainter secondary dust disk.

This 2003 Hubble view of the area surrounding Beta Pictoris shows a main dust disk and a much fainter secondary disk. (A coronagraph was used to block out the light from the bright star in the center.)

The recent announcement of the discovery of over 1,200 worlds whirling around other stars has accustomed us to the reality of our Milky Way galaxy being chock full of planets. These exoplanets, as they’re called, were discovered by NASA’s Kepler space observatory.

But the granddaddy of the ballooning field of exoplanet research is the blazing star Beta Pictoris, located 63 light-years away in the far southern sky.

Thirty eight years ago — long before exoplanets were ever discovered — the star got astronomers’ attention because it has an odd excess of infrared radiation (IR) for a star of its temperature.

This was identified as the IR glow of a warm dust disk encircling the star. Astronomers know that newborn planets generate dust through collisions. Take a look at our solar system: The Moon was born from a grazing blow to the Earth by a Mars-sized embryonic planet.

Where there’s dust, there could be planets too, astronomers reasoned.

In the early 1980s, a ground-based telescope revealed a pair of spike-like appendages on either side of the star. This was interpreted as an edge-on dust disk.

Beta Pic immediately became the poster child for the possibility of exoplanets (which weren’t first discovered until 1995). All through the 1980s, the somewhat abstruse Beta Pictoris photo appeared in nearly every introductory astronomy textbook and popular space books.

Through the 1990s, the Hubble Space Telescope gleaned spectroscopic evidence for a snowstorm of comets whirling around Beta Pictoris. Soon, crisp Hubble pictures showed there were in fact two disks around the star, perhaps altered by the gravitational tug of an unseen planet. Hubble had accomplished far more than anyone could have ever imagined when the Beta Pictoris disk was first imaged.

In 2009, astronomers at the European Southern Observatory photographed a planet near the star.

Now, new observations show that the planet is indeed orbiting the star according to laws of planetary motion formulated by Johannes Kepler nearly 400 years ago.

Today the much-lauded Beta Pictoris system is like an aging movie star whose celebrity status has been diminished. The Hubble Space Telescope made similar observations in 2004 and 2006 when it photographed a hot, young, Jupiter-sized planet orbiting the star Fomalhaut. The planet was seen moving along its orbit at a rate that Kepler himself would have easily calculated.

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