On May 16, 1969, the Soviet spacecraft Venera 5 reached Venus. Since 1961, the Soviet Union tried to reach the second planet of our solar system. The first two Venera spacecraft performed flyby missions and the third became the first man made object to impact another planet. Venera 5 was the third spacecraft to land (read crash) on the surface. It was crushed under the pressure of the atmosphere at an altitude of 22 miles, but not before it sent nearly an hour's worth of valuable data.

The Venera program would finally make a successful touchdown on Venus during the Venera 7 mission in December, 1970. Find out what else occurred on this day in science history.

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Here's a quick and easy science project you can do: make a cloud inside a bottle. Clouds form when water vapor forms tiny visible droplets. This results from cooling the vapor. It helps to provide particles around which the water can liquefy. In this project, we'll use smoke to help form a cloud.

Cloud in a Bottle Materials

• 1-liter bottle
• warm water
• match

Let's Make Clouds

1. Pour just enough warm water in the bottle to cover the bottom of the container.
2. Light the match and place the match head inside the bottle.
3. Allow the bottle to fill with smoke.
4. Cap the bottle.
5. Squeeze the bottle really hard a few times. When you release the bottle, you should see the cloud form. It may disappear between 'squeezes'.

The Other Way to Do It

Ok, here's the ideal gas law:

PV = nRT, where P is pressure, V is volume, n is number of moles, R is a constant, and T is temperature.

If we're not changing the amount of gas (as in a closed container) then if you raise the pressure, the only way for the temperature of the gas to be unchanged is by decreasing the container volume proportionally. I wasn't sure I could squeeze the bottle hard enough to achieve this (or that it would bounce back) and I wanted a really dense cloud for the photograph so I did the not-as-child-friendly version of this demonstration (still pretty safe). I poured water from my coffeemaker into the bottom of the bottle. Instant cloud! (... and a slight melting of the plastic) I couldn't find any matches, so I lit a strip of cardboard on fire, inserted it into the bottle, and let the bottle get nice and smoky (and melted more plastic... you can see the deformation in the photo). Dense cloud, no squeezing required, though of course it still worked.

How Clouds Form

Molecules of water vapor will bounce around like molecules of other gases unless you give them a reason to stick together. Cooling the vapor slows the molecules down, so they have less kinetic energy and more time to interact with each other. How do you cool the vapor? When you squeeze the bottle, you compress the gas and increase its temperature. Releasing the container lets the gas expand, which causes its temperature to go down. Real clouds form as warm air rises. As air gets higher, its pressure is reduced. The air expands, which causes it to cool. As it cools below the dew point, water vapor forms the droplets we see as clouds. Smoke acts the same in the atmosphere as it does in the bottle. Other nucleation particles include dust, pollution, dirt, and even bacteria.

Cloud Seeding Hurricanes | Make Water Vapor Fog

The Daily What alerted me to a chemistry kit that advertises it contains no chemicals. Of course, everything is a chemical, so unless the box encases a vacuum, there's some false advertising here. It's worth noting the kit contains small magnets, which while not chemicals (according to the manufacturer) may cause injury or death if swallowed.

Personally, I'm glad today's chemistry kits don't contain mercury or other excessively hazardous materials, but I think too much has been removed from chemistry kits made for teens and adults. A modern chemistry kit isn't much different from a kitchen cupboard in terms of the chemicals it contains. While these chemicals can be used to perform a wide range of interesting experiments, serious investigators are left wanting something more. Further, chemistry kits "without chemicals" offend me, since they bolster the impression that all chemicals are dangerous. I like the kits that contain age-appropriate chemicals, with cautions regarding proper handling of the contents.

What's your opinion? Here's a poll you can take, plus you can tell the world whether you think chemistry kits are too dangerous.

Edward Pickering was an American astronomer who was director of the Harvard College Observatory from 1877 to his death in 1919. He is famous for becoming frustrated with the male assistants and students and declaring his maid could do a better job. His maid at the time was a Scottish immigrant named Williamina Fleming. Pickering started using Williamina for clerical work, organizing the spectral photographs taken at the observatory. Over time, she cataloged over 10,000 stars and discovered 222 variable stars and several nebulae, including the Horsehead Nebula.

May 15^th is Williamina's birthday. She was so successful at her job that Pickering hired many more women to do the mathematical work and classifications with Mrs. Fleming in charge of them all. Harvard made her Curator of Astronomical Photographs, the first official position given to a woman.

Find out what else occurred on this day in science history.

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