# Opening scene from Contact

The opening scene for Contact is quite possibly the best opening scene in a movie, ever. (When you watch this clip, it’s recommended that you change the resolution to 720p HD and turn up the volume.)

This is a wonderful illustration of the principle that distance (and motion) is equivalent to time. The speed of any signal, whether light or sound or carrier pigeon, is always finite. It takes time for a signal to travel the distance between the source and the receiver, so this means the signal is always telling us something about the past. Back in the days when people communicated with each other using letters, it took a week or two to receive them, depending on how far they had to travel; when the recipients read those letters, they were always reading about something that was recent to the sender, but already one or two weeks in the past for the recipient. Similarly, when we look at the star Betelgeuse, the light that we see has taken time to travel the distance between Betelgeuse and the Earth, and so we are seeing it as it was in the past (at a distance of 400 trillion miles and with light traveling at a speed of 186,000 miles per hour, we are seeing Betelgeuse as it was 640 years in the past). Conveniently, such vast distances are often expressed in units of light-years (the distance light travels in a year), which also tell us at what point in cosmic history we are observing something.

In the opening scene of Contact, the further away we travel from Earth, the older the radio transmissions become. We first hear contemporary (for 1997) music, then the soundtrack gradually shifts to music and news from further and further in our past. Once we get beyond a certain point we hear static, then silence.

But sounds don’t travel through space, I hear some of you saying. True. However, radio signals are light waves, not sound waves. The radio waves, which carry information, are transmitted in all directions and are picked up by a receiver with an antenna (say, an AM/FM radio) that converts the radio signal into the sound you hear. So, in principle, anyone who might be not too far out in space could pick up our terrestrial radio and television signals and learn all kinds of interesting things about the inhabitants of Earth.

Perhaps you are wondering from how far out in space someone could receive intelligent signals from Earth. The scale of the Contact sequence isn’t quite right—it was fudged a bit for creative/dramatic purposes. The truth is, if aliens are zipping past Pluto at this moment, they would receive transmissions from Earth that are from only five and a half hours in the past. Little Green Men near our closest stellar neighbor, Alpha Centauri, would receive transmissions from the year 2009. Civilizations on a planet orbiting the star Alpha Mensae (33 light-years away), however, might catch old episodes of Dallas. Someone passing close to the star 51 Pegasi (50 light-years away) might be aware that someone named John F. Kennedy has been assassinated in a place called Dallas. An alien near the star Regulus (77 light-years away) could be watching images of Hitler opening the Olympic Games in Berlin. Further still, near the star Eta Herculis (112 light-years away), curious beings might just now be detecting Marconi’s radio transmissions. Beyond this distance, the Earth is silent. Considering that our Milky Way galaxy is more than 100,000 light-years across, we’ve barely announced our existence to the neighbors down the street. Not that this is entirely lamentable. Personally, I find it comforting that so little of the universe is aware of the Kardashians.

# The universe is a little older than previously thought

Scientists using data from the ESA Planck mission have measured the age of the universe to be a little older — about 100 million years older — than previously thought. The official age, based on measurements of the cosmic microwave background, is now 13.8 billion years. Also, the proportions of matter and dark energy have changed a little, with slightly more matter (‘normal’ matter + dark matter) and slightly less dark energy than previously measured.

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# Voyager 1 is on a “magnetic highway”

Popular media reports that the Voyager 1 probe has left the solar system are premature, according to NASA. Back in December, NASA reported that Voyager 1, which was launched in 1977, had entered a region known as a “magnetic highway” that is a boundary between the solar system and interstellar space. The magnetic highway is a region where the magnetic field lines of the Sun meet the magnetic field lines of interstellar space, permitting charged particles to stream into and out of the solar system. Voyager scientists expect the spacecraft to cross this highway and enter interstellar space soon, but have seen no evidence for this crossing yet.

Update: xkcd comments on Voyager 1’s latest journey out of the solar system:

So far Voyager 1 has ‘left the Solar System’ by passing through the termination shock three times, the heliopause twice, and once each through the heliosheath, heliosphere, heliodrome, auroral discontinuity, Heaviside layer, trans-Neptunian panic zone, magnetogap, US Census Bureau Solar System statistical boundary, Kuiper gauntlet, Oort void, and crystal sphere holding the fixed stars.

# Of knitting needles and auroras

Check out this video shot on board the International Space Station. It shows a polyethylene knitting needle that has been given a net charge and what happens as water droplets are fired at it. This phenomenon is similar to the process that generates terrestrial auroras, as charged particles from the Sun swirl around the Earth’s magnetic poles and produce radiation.

# Travel the Earth in 60 seconds

Science teacher James Drake assembled this time-lapse video from a series of hundreds of photographs taken by astronauts aboard the International Space Station. See if you can identify geographical features (a full listing is in the YouTube description). Note the yellow line of Earth’s ionosphere and the flashes of lightning.

# New Mars rover will look for signs of liquid water

An enhanced-color image of the Gale crater (Credit: NASA/Steven Hobbs)

Scientists at NASA’s Mars Science Laboratory have selected the crater ‘Gale’ as the landing site of the rover, Curiosity, when it visits the Red Planet next year to search for signs of historical liquid water.

This will mark the 15th time the U.S. has visited Mars since it was first photographed by the Mariner 4 orbiter in 19651. Mars is of great interest to scientists, not only because of its proximity to Earth (it’s our second-closest planetary neighbor after Venus), but because the Red Planet has been the subject of intense speculation about the presence of alien life for over 200 years.

Speculation about Martian life started in the late 1700s with German-British astronomers and siblings, William and Caroline Herschel, who observed the Red Planet and noticed that it had some features in common with Earth, including axis tilt, length of day, and seasonal changes in its appearance. Moved by these similarities, William speculated that Mars had inhabitants. From his address to the Royal Society in 1784:

It appears that this planet is not without considerable atmosphere; for besides the permanent spots on the surface, I have often noticed occasional changes of partial bright belts; and also once a darkish one… These alterations we can hardly ascribe to any other cause than the variable disposition of clouds and vapors floating in the atmosphere of the planet… Mars has a considerable but modest atmosphere, so that its inhabitants probably enjoy a situation in many respects similar to our own.

In the late 1800s, Italian astronomer Giovanni Schiaparelli added to this speculation when he observed what he thought were canals on the surface of Mars. Schiaparelli’s observations inspired the construction of the Lowell Observatory in Flagstaff, Arizona to further study the phenomena. Astronomer Percival Lowell, who founded the observatory, became convinced that the canals were signs of advanced, intelligent life on Mars. From there, it wasn’t much of a leap to science fiction stories about Martian life, including H. G. Wells’ dark tale, The War of the Worlds, and C. S. Lewis’ Christian-themed Out of the Silent Planet.

Despite the fervor over possible Martian life, there were astronomers who questioned whether there was any credible visual evidence for the canals. These questions persisted until Mariner 4 was sent to Mars and failed to detect any signs of the infamous canals. Since then, the focus on the search for life on Mars has shifted to evidence for historical, probably much more primitive, forms of life. If such life ever existed on Mars, it would have required the presence of liquid water, which is why scientists are so eager to find signs of the stuff.

# Atlantis lands, space shuttle program comes to a close

Well, that’s that. Space Shuttle Atlantis has landed safely, bringing a close to NASA’s space shuttle program after more than 30 years. It was inevitable and necessary, but depressing nonetheless. I can’t bring myself to say more on the subject, so I’ll leave you with the encouraging words of Bill Whittle on the future of space travel.

# Final voyage of Atlantis marks the end of the shuttle program

Space Shuttle Atlantis roared into space at 11:30 EDT this morning, marking the final launch in a program that started three decades ago.

This pretty well sums up my sentiments on this day:

“It’s kind of a letdown knowing we now have to rely on foreign interests” to launch American astronauts into space, said Terry Deguentz, a firefighter from St. Louis who said he was friends with one of Atlantis’s astronauts, mission specialist Sandy Magnus. “American ingenuity has been downplayed in the last decade. Once we let it go, I wonder if we can get it back.”