With the year of rooster passing by and the year ofdog approaching， in the wind-blowingand snowy February， we ushered in another spring festival.

When I am writing this article， many people in our country who work outside their hometowns are heading towardtheir home despite the sudden heavy blizzard that blocks the traffic and the freezing coldness. The passenger flow data in one and another traffic hub reflects our longing for family reunions. It seems that they go home， tired while happy， only to have a dinner with the whole family， which symbolizes family reunion， while the bell and the firecrackers ring for the new year.

This ritual step has passed down right from the remote farming era， through the noisy industrialization era all the way into the current society featuring speed and efficiency. For the sake of reunion， we would rather put aside urgent matters for a while and make some concessions in terms of efficiency.

The freezing coldness of winter seems to be connected with the warmth of reunion by an invisible link. Coldness and lack of sunshine will inevitably produce a sense of loneliness and desolation； such feeling will be intensified by toil， coldness and loneliness when one works at somewhere unfamiliar and far away from home.

There is an example in extreme situations that may well illustrate this state of mind. At the end of 1958， Hunter Henry Rudy spent a polar night alone in the Svalbard Islands，nearly 80 degrees north latitude.After the spring， when asked by an expedition team "Arent you afraid of the night？"， he spoke in a rather poetic language of his feeling： "I watched the night wrapped up the sun anddrown it in a mixture of scarlet and blue and green； polar nights （like beasts） fluttered upon m， exhaled the chill of death， and silenced whispers in my ears.” Every word of him reveals a sense of longing for the earth to regain its warmth.

Since then， with the progress of scientific research， we have become more and more acutely aware of the mechanism behind this phenomenon. We know why we will long for warm things involuntarily in winter， which may be the relaxing spa， the delicious hot meals， the beverages， and of course family reunion. The last one has been part of our instincts， because humans have always been the social animals.

The old hearth may be replaced by modern electrical heating equipment； our residence could move from the village of the communityto the bustling city， and even to winter polar regions that rarely share the sunshine. But what will not change is our longing for the warmth of reunion between our loved ones. We may have attached a great many meanings to holidays， but as we penetrate deeper， we will see from the bottom of our hearts the longing for our hometowns and reunion， because it symbolizes protection and support without danger and fear.

This issue ofKnowledge is Powerwill show you the charm of various "Spring Festival elements" and the science behind them. Irrelevant as the couplet on the door， the food on the dining table， different folk customs of the Spring Festival of all nationalities， the hot spring brought by the geothermal mineral and the snow and ice art of the frozen world may be， they reflect the same inner world of all mankind in the winter.