Hydrogen
In balloons, it is desirable to use the lightest possible gas. Nitrogen is a relatively heavy gas with Atomic mass no. of 14. Instead, a much lighter gas, Helium, is used. It has an Atomic mass no. of 4. Hydrogen was used a long time ago, since it was the lightest gas. But due to its explosive nature, it is no longer used.
helium or hydrogen
Balloons and bladders are both flexible containers that can expand and contract to hold air or liquid. They are both used in various applications such as decorations, transportation, and storage. Additionally, both balloons and bladders can pop or burst if they are subjected to too much pressure.
Rockets have been widely used by many military forces for at least 300 years. One hundred years ago in WW1 there was a limited amount of rocket artillery used, and the French air force used rockets mounted on aircraft to attack balloons .
Chinese were the first to design hot air balloons. They were thought to have made it more than 600 years ago. There are pictures showing this.
It should be hyphenated if used as a noun clause, but not if used as an adjective
700 yrs ago give or take
There used to be but they closed about a year ago.
1000000000 minutes ago would be approximately 1902 AD.
Ten years ago they was. Not now. I still have a old set and they are very nice. If you can find a set buy them.
558 years ago.
What was the year 1400 years ago and how it is A.D?