| "All the news that's fit to link." | Last updated May 16, 1996 |
 Rearchers at the National Institute of Allergy and Infectious Diseases have identified a previously unknown protein called fusin that must be present for the AIDS virus to infect white blood cells. Although this discovery may not help those already infected with the AIDS virus, it does solve a problem researchers have been working on for ten years, one that has slowed the search for a cure. Scientists believe this discovery to be a significant milestone in AIDS research. It is hoped that this discovery could eventually lead to new drugs and vaccines against HIV, the virus that causes AIDS. "What's News" asked Exploratorium Director of Life Sciences Charles Carlson to give his thoughts on this significant development in AIDS research.
Click HERE to download the RealAudio player. Related Sites USA TODAY ONLINE: AIDS discovery hailed as research milestone S.F. Chronicle: Milestone in AIDS research What About AIDS? Science, Art & Human Stories
 "What's New" has come a long way since our first issue in October 1995. With seven back issues and more issues on the way, it seemed natural to create a better way of searching past issues for information. We now have a search function that lets you "browse" back issues with ease. Just type in the word or phrase you are looking for, and you can find out whether it's been in "What's New." Using the radio buttons below, you have the option of searching the whole site or just the "News" site. We hope this feature helps you find what you're looking for on our server.
"What's New in in the World of Science" is published the middle of every month. Remember to check back next month and see "What's New"!
Please send mail or comments to your editor: |
According to NASA, these two sets of new results "yield ranges for the age of the Universe from nine to twelve billion years and eleven to fourteen billion years, respectively." The researchers are attempting to measure the Hubble constant to within 10 percent accuracy.
The Hubble constant, devised by astronomer Edwin Hubble, is a value that calculates the rate of the universe's expansion. By knowing how fast the universe is expanding, scientists can estimate its age.
"What's News" asked Exploratorium physicist Dr. Linda Shore to explain the Hubble constant and the impact of this new research.
About Edwin Hubble (and the Hubble constant)
HST Greatest Hits 1990-1995 Gallery
Have you ever noticed that when someone passes you while honking a car horn, the tone changes from a high note as the car approaches you to a low note as it recedes from you? If you were in the car, traveling with the honking horn, there would be no difference; the horn would always sound the same. You hear the same effect when watching a car race on television. As a car passes by a stationary microphone, its engine sounds like the car is slowing down. (What a silly thing for the driver to do!) When the television station switches to a camera and microphone INSIDE the car, you hear no change in the engine speed at that point. This phenomenon, called the Doppler effect, occurs for all types of waves, whether sound waves, water waves, or light waves.
Find a long street and have a friend drive a car to the far end. Position yourself near the center of the block and signal your friend to drive past you at about 25 mph while blowing the horn continuously. (You'd better invite the neighbors to participate in this experiment!) Notice the change in the horn's sound. Now try driving the car yourself while continuously honking the horn. Notice that now there is NO change. If you or your friend have a loud musical instrument (a tuba, trombone, or trumpet will do) have your friend play a single note while standing in the middle of the block as you drive by in the car. Notice the change in pitch.
Click here to hear the Doppler effect (a Volvo horn blowing while the car is moving at 30 mph).
If the source of the sound is moving, it chases after its own waves in front and runs away from the waves behind it. The waves in front are therefore closer together, and when they hit you, they vibrate your eardrum more rapidly and you hear a higher note. As the car recedes from you, your eardrum is vibrated by more widely spaced waves, and you hear a lower note.
If you approach a stationary source of sound, you run into the waves more often and you hear a higher note. When you move away from the stationary source, the waves have to catch up to you, hitting you less often and causing you to hear a lower note. An animated shock-wave representation of the Doppler effect can be found in the Exploratorium's Exhibit/Phenomenon Cross-Reference.
This effect also occurs with light waves, but you have to travel very, very fast to notice. When you approach a source of light (or when it approaches you), the waves are squished together and the light appears to be bluer that before. If you recede from a source (or it recedes from you, as all galaxies recede from our point of view on Earth), the light waves are stretched to redder wavelengths. These Doppler shifts are called "blue" and "red" shifts, respectively. (Sorry, but you would have to approach that red traffic light at 191 million miles per second to make it appear green!)
Ron Hipschman
Paul showed off some of the experiments he does with the many teachers who visit the Exploratorium. If you missed the show, we're sorry, but you'll have to wait for the reruns. Congratulations to Paul for a job well done!
|
 |
 |
 |
| The Learning Studio | The Exploratorium |
