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حافظه چیست؟ از یک نظر؛ تمامی قوانین بقا، مثل قانون بقای انرژی و ... ، حافظه جهان هستنـد. مطابق این قانون، جهان به یاد دارد که قبل، بعد و احتمالا در حین هر فعل و انفعال و تقابل میان میان اشیا چه میزان انرژی داشته است. اگر حافظه به نوعی «انرژی ذخیره شده» یا انرژی پتانسیل باشد، آن وقت تغییـر در نیروهایی که ما را به هم پیوند می دهند؛ یعنی نیروهای الکتریکی و گرانشی (شاید هم نیروهای هسته ای)، می تواند منجر به بروز خاطره شود.

New measurements of Mars' South Polar Region indicate extensive frozen water. The polar region contains enough frozen water to cover the whole planet in a liquid layer approximately 11 meters (36 feet) deep. A joint NASA- Italian Space Agency instrument on the European Space Agency's Mars Express spacecraft provided these data.

This new estimate comes from mapping the thickness of the ice. The Mars Express orbiter's radar instrument has made more than 300 virtual slices through layered deposits covering the pole to map the ice. The radar sees through icy layers to the lower boundary, which is as deep as 3.7 kilometers (2.3 miles) below the surface.

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Think of a guitar string that has been tuned by stretching the string under tension across the guitar. Depending on how the string is plucked and how much tension is in the string, different musical notes will be created by the string. These musical notes could be said to be excitation modes of that guitar string under tension.
In a similar manner, in string theory, the elementary particles we observe in particle accelerators could be thought of as the "musical notes" or excitation modes of elementary strings.